In the art of petroleum production, a borehole is drilled into the earth through the oil or gas producing subterranean formation or, for some purposes, through a water bearing formation or a formation into which water or gas is to be injected. Once produced from the borehole, oil and gas can be transported using pipelines.
Completion of a well may be carried out in a number of ways dependent upon the nature of the formation of interest. Where the formation itself or formations above the formation of interest have a tendency to disintegrate and/or cave into the hole, a cylindrical metallic casing is normally set in the well through the formation of interest and the cylindrical metallic casing is then perforated adjacent the formation of interest.
In order to produce formation fluids or gases, completion strings are arranged in the borehole. Such a completion string generally comes as a production tubing which comprises a plurality if different components such as, e.g. safety valves, sliding side doors, side pocket mandrels etc. . . . .
Similarly, a pipeline comes as a production tubing which may comprise a plurality of different components such as e.g. metallic tubes, pipeline valves etc. . . . .
In any event, after a period of production, injection or transportation of fluids or gases, there is a tendency for the components of the completion string and/or pipelines to become plugged with various types of residues. For example, organic residues like paraffin, asphalts and other gummy residues of petroleum origin often cause plugging problems.
Usually these deposits can cause significant problems, because of their composition and the fact that they can precipitate under certain conditions (pressure, temperature, composition). These materials of mineral or organic origins either together with chemicals from water, normally produced with the oil, such as, calcium carbonate, calcium sulfate, barium sulfate, sulfur and the like, or such chemicals themselves have a tendency to form extremely hard deposits on different parts of the components.
Such deposits can adhere to various components in a borehole wellbore or a pipeline, restricting their use seriously and/or reducing or completely preventing the flow of fluids or gases through the completion string or the pipeline. For example, deposits may prevent opening or closing safety valves or sliding side doors, etc
Such deposits are difficult to dissolve by known chemical means or to dislodge by known mechanical means. For example, chemical treatments, such as, treatments with acids, surface active agents and the like have been utilized in order to clean out scaled components. However, such techniques, while less expensive than a complete workover, are substantially less effective, since they are incapable, in most cases, of dissolving significant amounts of the plugging materials. Another technique, which can be classified as a mechanical technique and has also been suggested for the purpose of cleaning components, includes using brushes, scrapers or pigs. Such equipment allows only removing most of the encrusted deposits in areas of the components which are easily accessible. However, brushes, scrapers or pigs are quite inefficient removing encrusted deposits in areas of the components accessible with difficulty or inaccessible.
Consequently, it is often necessary to rework the well and replace one or several components of the completion string or the pipeline. Such tactics are, of course, both time-consuming and expensive.
It is therefore an object of the present invention to provide an improved method and device for efficiently and effectively cleaning components of a completion string arranged in a borehole extending into the earth or of a transportation pipeline. Another and further object of the present invention is to provide an improved method and device for removing deposits encrusted on components of a completion string arranged in a borehole or of a transportation pipeline, in particular in areas of the components which are accessible with difficulty or inaccessible to mechanical means such as brushes, scrapers or pigs. Yet another object of the present invention is to provide an improved method and device for increasing the production of fluids or gases from a subsurface earth formation or increasing the injectivity of fluids or gases into such formations or the transportation of fluids or gases into a pipeline.